CVE-2021-20491 [Medium] | Out-of-bounds Write in Spectrum Protect

IBM Spectrum Protect Server 7.1 and 8.1 is subject to a stack-based buffer overflow caused by improper bounds checking during the parsing of commands. By issuing such a command with an improper parameter, an authorized administrator could overflow a buffer and cause the server to crash. IBM X-Force ID: 197792.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	0.05%	0.26%	+0.21%
2	2025-03-30	0.08%	0.05%	-0.03%
3	2025-03-29	—	0.08%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-15

0.05%

0.26%

+0.21%

2025-03-30

0.08%

0.05%

-0.03%

2025-03-29

—

0.08%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
4.4	3.1	MEDIUM	`CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H` Click to expand Attack vector (AV:L) They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:H) They need powerful rights—admin, root, or similar—before this pays off. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	0.8	3.6	[email protected]
4.4	3.0	MEDIUM	`CVSS:3.0/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H` Click to expand Attack vector (AV:L) They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:H) They need powerful rights—admin, root, or similar—before this pays off. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	0.8	3.6	[email protected]
2.1	2.0	LOW	`AV:L/AC:L/Au:N/C:N/I:N/A:P` Click to expand Access vector (AV:L) Requires local access to the target system. Access complexity (AC:L) Exploitation conditions are straightforward and predictable. Authentication (AU:N) No authentication is required. Confidentiality impact (C:N) No confidentiality impact. Integrity impact (I:N) No integrity impact. Availability impact (A:P) Partial availability impact.	3.9	2.9	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

4.4

3.1

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H Click to expand

Attack vector (AV:L): They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:H): They need powerful rights—admin, root, or similar—before this pays off.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

0.8

3.6

[email protected]

4.4

3.0

MEDIUM

CVSS:3.0/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H Click to expand

Attack vector (AV:L): They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:H): They need powerful rights—admin, root, or similar—before this pays off.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

0.8

3.6

[email protected]

2.1

2.0

LOW

AV:L/AC:L/Au:N/C:N/I:N/A:P Click to expand

Access vector (AV:L): Requires local access to the target system.
Access complexity (AC:L): Exploitation conditions are straightforward and predictable.
Authentication (AU:N): No authentication is required.
Confidentiality impact (C:N): No confidentiality impact.
Integrity impact (I:N): No integrity impact.
Availability impact (A:P): Partial availability impact.

3.9

2.9

[email protected]

Affected software / configurations for CVE-2021-20491

Vendor	Product	Version	Raw CPE
ibm	spectrum_protect	>= 7.1.0.000, < 7.1.13	cpe:2.3:a:ibm:spectrum_protect::::::::
ibm	spectrum_protect	>= 8.1.0.000, <= 8.1.10.100	cpe:2.3:a:ibm:spectrum_protect::::::::
ibm	spectrum_protect	8.1.11.000	cpe:2.3:a:ibm:spectrum_protect:8.1.11.000:::::::*

References for CVE-2021-20491

URL	Tags
https://exchange.xforce.ibmcloud.com/vulnerabilities/197792	VDB Entry Vendor Advisory
https://www.ibm.com/support/pages/node/6442993	Patch Vendor Advisory

URL

CVE-2021-20491

Exploit prediction scoring system (EPSS) score for CVE-2021-20491

Common vulnerability scoring system (CVSS) metrics for CVE-2021-20491

Weakness enumeration for CVE-2021-20491

Affected software / configurations for CVE-2021-20491

References for CVE-2021-20491